Blackout Puzzles

Each of the puzzles below is actually 3 puzzles in 1. First black out 2 squares so that the remaining equation is true. Then black out 3 squares to make a correct equation. Then do it with 4 squares. (The standard order of operations is used: multiplication and division are done before addition and subtraction. Only whole numbers are used, though the results might be negative.)


1.
2.


3.
4.


5.
6.


7.
8.


9.
10.


11.
12.


The Solutions are here.